Thixotropic thread lubricant



3,06%,337 THTXQTRQPMZ THREAT) LUBRHCANT Lloyd it. Alien, Eelmont, andDudley H. Woodard, Cambridge, Mass, assignors, by rnesne assignments, toKenmore Research Company, Framingham, Mass., a corporation of (thin NoDrawing. Filed June 1, 1956, Ser. No. 588,626 3 (Claims. (Cl. 252-495)This invention, relating as indicated to thixotropic lubricants, isparticularly directed to a thixotropic thread lubricant adaptable foruse over a Wide range of temperatures, especially under 400 F. Thelubricant is characterized by reducing the galling between threadedmembers of stainless steel, titanium, aluminum and the like, and employsa relatively high concentration of powdered polytetrafiuoroethylene,i.e., Teflon, and a mild pressure lubricant in a thixotropie gellingagent, such as Bentone 34.

in the prior art, various types of lubricants, greases and threadlubricants have been known, but these have had certain limitingconditions and have not had as low a co-eflicient of friction as wasdesirable, particularly over a wide temperature range.

This invention relates, then, to a thread lubricant having a mildpressure, wetting type lubricating oil, such as castor oil with anorganophilic gelling agent, such as Bentone 34, and powderedpolytetrafiuoroethylene, which will be referred to hereinafter forsimplicity as Teflon.

An object of this invention is to provide a new and improved lubricant,particularly a thread lubricant, having a spacer or cushioning elementwhich will prevent locking of the threads A further object of thisinvention is to provide a nonsettling thixotropic lubricant which willhave permanently suspended therein spacer particles of small size ofpolytetrafiuoroethylene to cushion the locking action of the threads.

In connection with this invention, Teflon is employed because of itsgood anti-friction properties, and it is intended to be used in specificsizes, viz., 1 to 20 microns in "dimension, i.e., 1 to 20 millionths ofa meter. This will be less than the average (root mean square) size ofthe asperites of the threaded particles, yet small enough to filldepressions on the tops of the asperites.

in this connection Teflon is characterized by its low modulus ofelasticity and its extremely low co-efflcient of friction. The modulusof elasticity of Teflon is important because it means that each of theselittle particles of Teflon serves as a rider or cushioning element forthe asperite and can be deformed by the asperite rather than serving asrigid particles which would increase the friction. When they are smallenough and have a low enough modulus, they tend to bend elastically andpermit the surfaces to glide with respect to one an other. A partialexplanation of the low co-eflicient of friction of Teflon with steel maybe due to the low surface shear stress of Teflon.

Further in connection with this composition of Teflon particles of smallsize in a thixotropic lubricant containing a fatty acid base, mildpressure lubricating oil, it is intended to use castor oil. Castor oilis a good lubricant in that it bonds to the metallic surfaces, formingboth a physical and a chemi-sorbed bond. With this lubricant, we intendto use a thixotropic gelling agent, such as Bentone 34, and Teflon.

The Teflon serves as a lubricating medium in itself, having a very lowco-eflicient of friction. However, it would be ineffective if not heldin position, i.e., in the thixotropic thread lubricant, so that it isready to perform its function at the surface of the moving or gellingparts. It further will be held to the surface by the wetting action ofthe lubricating material such as castor oil. The combination of thethixotropic gelling agent and the mild pressure lubricant, which in thisparticular instance is a castor oil-Bentone mixture, has a considerablylower frictional co-eflicient with the Teflon than without it.

It will be seen from the foregoing that the Teflon in this combinationacts in several ways. First, it acts as a barrier particle or spacerelement so that the metal particle, such as steel, never would rubagainst the oppositely disposed surface and, in performing thisfunction, it reduces the co-efiicient of friction. The material itselfand in combination with the mild pressure lubricant has a particularlylow co-eflicient of friction with a metal such as steel. The Teflonstays in position because of the wetting action of the mild pressurelubricant. The thixotropic gelling agent further increases the adherenceof the mild pressure lubricant to the Teflon.

Under tests of threaded parts employing this combination of materials,the galling was greatly reduced by the action described.

As an example of these compositions and how they are made, the followingis given. A standard composition for one batch might be 2000 cc. ofcastor oil; 160 grams of a thixotropic gelling agent, such as Bentone34, which is dimethyldioctadecyl ammonium bentonite; cc. of acetone; and730 grams of Teflon. The followlog are examples of the ranges that maybe employed:

From the foregoing, it will be seen that Teflon may be used from 20 to50 percent of the mixture with the balance being fluid, principallylubricating oil and the thixotropic gelling agent.

in these compositions, the powdered Teflon is processed as follows.Teflon is stored in a deep-freeze to prevent agglomeration. It isscraped through a stainless steel screen into the media, castor oil.This is to break up any agglomeration that may have been formed. Ifparticles have been agglomerated in spite of these precautions by beingstored for a time at higher temperatures, it is recommended that theTeflon be frozen and screened again. A limited amount of mixing andstirring is performed in the castor oil after the Bentone and acetonehave been added, and these effectively make a thixotropic gelling agentand carrier for the Teflon; The Bentone 34 is, of course, anorganophilic gelling agent suitable for use with castor oil. AManton-Gaulin homogenizer was used to impart shear into the mixture. Itmay be possible under some conditions to use a high speed ball or rodmill, propeller agitation and heaters. A limited amount of agglomerationtakes place in this means, but does not seem to harm the final product,

As additional examples of the manner in which this invention may becarried out, the minimum and maximum ranges may be used and have beenused as examples, and compositions at varying points within thepreferred range have been used.

While only a few examples have been given herein, other thixotropiclubricants containing Teflon are satisfactory, that is, any lubricantthat is a wetting, mild pressure lubricant may be substituted for thecastor oil if suitable thixotropic agents may be used in connectiontherewith. Examples of these might be sperm oil, soybean oil or mineraloil. Examples of other fluids that may be used are the diester fluidsnormally used as plasticizers, examples of which are trioctyl phosphate,ethyl azelate and diethylhexyl sebacate.

In connection with thread lubricants, particularly in the food and drugindustries, we may use a lubricant of cottonseed oil and bentone, waterand bentonite, or other combinations of these materials which would notcontaminate the food or products with which they are used.

In addition to Teflon, We may also use Du Pont Teflon 3086, a stickypolytetrafluoroethylene polymer, in a proportion usually ranging from to40 percent of the T efion powder used, i.e., this material may be usedup to 40 percent of the entire mixture. As an example of this, we mayuse the following: castor oil, 1000 cc.; Teflon, 350 grams; Du PontTeflon 3086, 34 grams; Bentone 34-, 80 grams; acetone, 40 cc. andpossibly suitable coloring matter.

This invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments and examples are, therefore, considered in all respects tobe illustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are, therefore, intended to be embracedtherein.

We claim:

1. A thixotropic thread lubricant having a proportion f. of ingredientsas specified; castoroil 2000 cc. and additional ingredients in thefollowing varying proportions: dimethyldioctadecyl ammonium bentonitefrom to 400 grams; acetone from 25 to 200 cc.; finely powderedpolytetrafluoroethylene from 1 to 20 microns in size from about 500 to850 grams.

2. A thixotropic thread lubricant having a proportion of ingredients asspecified: castor oil 2000 cc.; dimethyldioctadecyl ammonium bentonitefrom 120 to 170 grams; actone from about to cc.; finely powderedpolytetrafluoroethylene from 1 to 20 microns in size from about 700 to800 grams.

3. A thixotropic thread lubricant having a proportion of ingredients asspecified: castor oil, 2000 cc.; dimethyldioetadecyl ammonium bentonite,of grams; acetone, 85 cc.; finely powdered polytetrafluoroethylene, from1 to 20 microns in size, 730 grams.

References Cited in the tile of this patent UNITED STATES PATENTS2,510,078 Compton et al June 6, 1950 2,510,112 Holbrook lune 6, 19502,531,440 iordan Nov. 28, 1950 2,644,802 Lontz July 7, 1953 2,679,479Peterson et al May 25, 1954 2,746,887 ONeil May 22, 1956 2,824,060 WhiteFeb. 18, 1958 2,833,720 Stratton May 6, 1958

1. A THIXOTROPIC THREAD LUBRICANT HAVING A PROPORTION OF INGREDIENTS ASSPECIFIED; CASTOR OIL 2000 CC. AND ADDITIONAL INGREDIENTS IN THEFOLLOWING VARYING PROPORTIONS: DIMETHYLDIOCTADECYL AMMONIUM BENTONITEFROM 50 TO 400 GRAMS; ACETONE FROM 25 TO 200 CC; FINELY POWDEREDPOLYTETRAFLUOROETHYLENE FROM 1 TO 20 MICRONS IN SIZE FROM ABOUT 500 TO850 GRAMS.